Septic Tanks

Septic Tanks for Domestic Use

A cross section of a septic tank.

JDP offers a range of septic tanks designed to settle the effluent, for situations where there is no mains drainage for the domestic sewage waste to discharge. Capacities available as standard: 2,800 litres - 54,000 litres. Other sizes available upon request.

Septic Tanks are historically the most common solution. However they do not treat the sewage, they only settle it. Because of even stricter environmental regulations septic tanks have become less common. The effluent cannot be discharged directly into a water course, and so a filter bed in a herringbone layout, constructed of smooth internal half perforated pipe, usually to EN1401-1 standard is required as part of the system to break down the biological matter. This means that the ground conditions and correct design and installation of the filter bed are critical to the performance of the system.

Features & Benefits

  • Low cost installation and maintenance
  • Lockable cover
  • Available in GRP or PE


The range of septic tanks provides an economic solution for anything from a single dwelling upwards, with the clarified effluent discharging to an underground filterbed system.

To ensure a septic tank is suitable the following information is essential:

  1. Discharge will not be directly into a water course (stream, lake etc).
  2. Consent to discharge from the EA (England & Wales) or SEPA (Scotland).
  3. Results of a percolation test based on BS 6297 recommendations to establish size of filter bed required.

NB. Do not be tempted to install a septic tank as a cheap option without the necessary consent. It could prove a very costly mistake.

All standard septic tanks are supplied with a 1m invert inlet. For deeper inverts heavy duty version should be used.

Septic Tank Care

How to care for your Septic Tank

If you jave just purchased a property which has a septic tank foul water system, there are many things that you can do to help prolong the life of the soakaway drainfield.

Divert Rainwater from the Septic Drainfield

  • A saturated drainfield can't absorb enough septic effluent.
  • Plan landscaping, roof gutters and surface drains so that excess water is diverted away from the soakaway area.

Don't overload the Septic Tank and Drainfield

The amount of water used in the home has increased dramatically over the last 20 years. If your septic tank pre-dates the current regulations, it is probably too small and struggling to cope with current flow rates. There are things you can do to reduce this problem:-

  • Repair leaking and dripping taps and toilets. Dual flush toilets often leak at the value after a period of time and need replacing.
  • Use aerators on taps and low-flow showers to help lower water consumption. Power showers just increase the volume of water used.
  • Change to a low water consumption washing machine and reduce water levels for small laundry loads.
  • Don't run a half-empty dishwasher
  • Toilets account for over 35% of all the water used in the home, water which overloads your soakaway. Fit dual flush toilets, use a 'Hippo' or, even better, convert your existing toilet to an 'eco' toilet with an INTERFLUSH conversion kit to reduce the amount of water needed to flush to the absolute minimum. The Interflush is a kit which fits on top of your WC siphon and connects to the front mounted flush handle. The toilet only flushes when the handle is held down, releasing the handle stops the flush (when pan is clear). It only uses the exact amount of water required, any less and the toilet would need flushing again. That is why nothing can flush a toilet with less water.

Keep trees away fromt the Septic System

  • Discourage root damage by keeping trees at least 30 metres away from the soakaway.
  • Trees with very aggressive roots, such as willows and poplars, should be even farther away from the system

Don't use your toilet and sink as a rubbish bin

  • Never flush cat litter, disposable nappies, pantie liners, tampons, paper towels, facial tissues, coffee grounds, or cigarrette ends down the toilet. They will clog your septic tank in less time than you might imagine.
  • Don't install a waste disposal unit as these can double the amount of solids going into the septic tank.

Be sensible with cleaning and disinfection products and what you pour down the sink

  • Overuse of Anti-Bacterials, disinfectants and heavy cleaners will kill the beneficial bacteria in the septic tank which digest your solids
  • Don't use anti-bacterial hand wash products as you are poisoning your septic tank bacteria with every wash
  • Do not pour grease or oil down the sink. Wipe greasy dishes with paper towels before washing.
  • Grease clogs the septic tank soakaway, and effectively 'waterproofs' it, making it impossible for soil to absorb liquids. If that happens you'll need a new soakaway.
  • White spirit, varnish, paint thinners, motor oils, petrol and other similar chemicals will ruin your septic system and are not easily broken down by soil bacteria. They will pollute groundwater.
  • Condensate from Condensing Boilers is very acidic and must not go into the foul drains.

Protect your soakaway

  • Do not drive over the soakaway, build a structure on top of it, or cover it with concrete or tarmac. Gravel is ok, but only for foot traffic.
  • Sow grass over the soakaway area, if possible, as grass takes up a lot of water.

Maintain your septic system

  • Solids must be pumped from the septic tank on an ANNUAL basis. Ignore the ignorant who tell you that 'septic tanks never need emptying' They only store 12 months worth of sludge and extending the 12 month emptying interval will ruin your soakaway!
  • Never lift the lid of a septic tank yourself, particularly if you are alone! The gases in the tank can overcome you very quickly and the bacteria are dangerous. Sewage workers must have regular vaccinations, including Hepatitis, Tetanus and Diptheria, to protect against them.


Siting the Unit

  1. British Standard BS: 6297-1983 recommends that sewage treatment works should be as far away from habitable buildings as is economically practicable. The direction of the prevailing wind should be considered in relation to any properties when siting the works. The sludge emptying contractor’s vehicle will probably have a maximum reach of 30 metres, but the depth from the ground level to the bottom of the tank must not exceed 5 metres.
  2. The installation should be carried out in accordance with the requirements of the Construction and Building Regulations. An inspection chamber should be installed upstream of the Treatment Plant. For discharge quality sampling purposes a sampling chamber can be provided (optional extra).


  • Read Full Installation Guide provided with delivery of goods.
  • Ensure Building Regulation approval.
  • Ensure consent of discharge is approved from the environment agency.
  • Ensure access for desludging tanker. (Building regulations suggest 30m max).
  • Check orientation and heights of inlet and outlets.
  • Use a pump to keep excavation clean and free from rising ground water during installation.


  • Use the correct backfill material.
  • Site tank at furthest practical location from habitable dwellings. Most building regulations recommend a minimum of 7m.
  • Fit the correct cover & frame (pedestrian duty) LOCKABLE.
  • Consider drainage falls, generally 1 in 60/70 between house and tank and max. 1 in 200 for filter bed system.
  • Lift the tank using adequate ropes or slings through both of the lugs fitted either side of the neck.


  • Subject the tank to impact or contact with sharp edges.
  • Add neck extensions to the tank, nor, build a brick manhole above the tank neck (as this increases burial depth of the tank beyond that which it was designed for). We do not recommend extending the neck of the tank under any circumstances.
  • Install tank deeper than the depth that the fitted neck will allow.
  • Install in trafficked areas without a suitable load bearing slab.
  • Site the tank so that it is subjected to excess ground pressure (e.g. sloping sites) or applied loads such as may be generated by the proximity of vehicular traffic.
  • Lift using only one of the lugs.
  • Fill an unsupported tank.

Service Agreement

Although of a minimal nature, it is advised that the plant is serviced periodically to help ensure many years of trouble-free operation. Service Agreements are available through your local JDP.

This is a requirement of the new PPG4 guidelines.